【摘要】 发生雷击故障时，接地体起到泄放故障电流的作用。由于雷电流幅值与瞬时频率均随注入时间快速变化，在雷电流作用下注流点附近土壤电气参数同时呈现时变性和频变性，忽略土壤的时变性和频变性会给接地体的冲击阻抗计算带来误差。针对土壤的频变性，通过希尔伯特黄变换对雷电流作时频域分解，用Viascro-Alipio土壤频变公式对土壤电阻率、介电常数等频变参数进行修正；针对土壤的时变性，将接地体分段，计算各段随时间变化的火花放电区域等效半径，建立了考虑土壤时变性和频变性的接地体暂态模型，并与文献真型试验结果对比验证其有效性。通过模型分析土壤频变性的影响，发现土壤电气参数的频变性会使接地体的冲击阻抗有所下降，在土壤电阻率高与冲击电流陡度大的情况下，其影响更加明显。更多还原

【Abstract】 The grounding body plays the role of discharging fault current when lightning strike fault occurs. Since the amplitude and instantaneous frequency of lightning current change rapidly with the injection time, the electrical parameters of the soil near the injection point under the action of lightning current show time-dependence and frequency-dependence characteristics. Ignoring the time-dependent and frequency-dependent electrical parameters of soil will bring great errors to the calculation of impulse impedance of lightning current acting on the grounding device. For the frequency-dependence of soil, the author decomposed the lightning current in time-frequency domain by Hilbert yellow transform, and corrected the frequency variability parameters such as soil resistivity and dielectric constant by Viascro-Alipio soil frequency variation formula; for the time-dependence of soil, the grounding body was segmented, then calculated the equivalent radius of spark discharge area in each segment with time, and established the transient model of grounding body considering the time-dependence and frequency-dependence of soil. The model’s validity is verified by comparing with the real type test results in the literature. By analyzing the effect of soil frequency variability through the model, it is found that the frequency-dependence of soil electrical parameters will cause the impact impedance of the grounding body to decrease, and the effect is more obvious in the case of high soil resistivity and high steepness of the inrush current.更多还原